Capacitors are widely used in integrated circuits. Among the most commonly used capacitors are Metal-Insulator-Metal (MIM) capacitors. A typical MIM capacitor includes a bottom plate, a top plate over the bottom plate, and an insulation layer between the top plate and the bottom plate. The bottom plate and the top plate are formed of conductive materials.
As is known in the art, the capacitance of a capacitor is proportional to its area and the dielectric constant (k) of the insulation layer, and is inversely proportional to the thickness of the insulation layer. Therefore, to increase the capacitance, it is preferable to increase the area and k value, and to reduce the thickness of the insulation layer. The thickness and the k value, however, are often limited by the technology used for forming the capacitor. For example, the thickness of the insulation layer is limited by the breakdown voltage. On the other hand, since the MIM capacitors are often formed in low-k dielectric layers, the ability to increase the k value is also limited. To solve these problems, Metal-Oxide-Metal (MOM) capacitors were also developed.